1. Field of the Invention
The present invention relates to a direct viewing type stereoscopic image display apparatus which can remove a moiré pattern to improve image quality.
2. Description of the Related Art
Generally, a three dimensional image is obtained by the principle of stereoscopic visual angle through two eyes of a person. Binocular parallax, which appears by two eyes spaced about 65 mm apart, is considered to be an important factor in the stereoscopic effect. A three dimensional image display apparatus includes a stereoscopic display apparatus using glasses and an auto-stereoscopic display apparatus. The auto-stereoscopic display apparatus obtains the three dimensional image by dividing the image into left and right images without using glasses. The auto-stereoscopic method includes a parallax barrier method and a lenticular method.
The parallax barrier method is a method for alternately printing images viewed by the left and right eyes in a longitudinal pattern shape and viewing the images using very thin longitudinal lines, that is, barriers. Thereby, the image is divided into the longitudinal pattern image which will enter the left eye and the longitudinal pattern image which will enter the right eye by the barriers, such that the images having different view points enter the left eye and the right eye, to form the three dimensional image.
FIG. 1A shows a conventional direct viewing type three dimensional image display apparatus. The display device 15 receives an image signal from the image signaling unit 10 and forms an image. The image is divided into a right eye RE image and a left eye LE image by the parallax barrier 17 to form the three dimensional image.
As shown in FIG. 1A, the parallax barrier 17 has alternating slits 17a and barriers 17b. The image is divided into the left eye image and the right eye image by the slits 17a to form the three dimensional image.
However, according to this method, since the image is formed by the slits 17a and the image is blocked by the barriers 17b, the left eye image L is formed only in even lines by the slit 17a, and black lines K are formed in the odd lines by the barrier 17b. Also, the right eye image R is formed only in odd lines by the slits 17a, and black lines K are formed in the even lines by the barrier 17b. Accordingly, there are problems in that the resolution and brightness of the display are low.
Also, a moiré pattern is generated by interference between a periodic pattern of the parallax barrier 17 and the image formed by the display device 15.
The moiré pattern appears due to interference that occurs when periodic spatial patterns overlap. FIG. 2 shows the generation of the moiré pattern. There is a problem that the image quality is reduced by the moiré pattern.